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Planetary News: Near Earth Objects (2006)

Asteroid Scores 2 on Torino Scale

3 March 2006

With little fanfare, the Jet Propulsion Laboratory's Near Earth Objects (NEO) program has listed asteroid 2004 VD17 as having the highest known threat of impacting Earth within the next century. The program's website listed the object as having a 1 in 1,400 chance of impacting Earth on May 4, 2102 or on the same date in 2104. The estimate is based on 691 observations of the asteroid, from November 7, 2004 to March 2, 2006.

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While the chances of an impact are slim, if one does occur the consequences would be grave. Based on its reflectivity, astronomers estimate that 2004 VD17 has a radius of 500 meters and a mass of 270 million metric tons. Orbital calculations indicate that the relative speed of 2004 VD17 at the time of impact would be 21.4 kilometers per second (13.3 miles per second). Given the asteroid's mass, this would translate to an impact energy of 15,000 megatons of TNT, which is greater than all the world’s nuclear arsenals combined.

Apophis (2004 MN4) speeds toward Earth
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An artist's depiction of Apophis (2004 MN4) speeding toward Earth
Credit: Michael Carroll

Because of the impact probability and the potential for widespread destruction, 2004 VD17 was assigned a value of 2 on the Torino scale, which measures the risk NEO's pose to Earth. The scale runs from 0 -- for no chance of impact -- to 10, which indicates certain impact likely to cause a global catastrophe. The only other object with a current assigned value above 0 is Apophis (2004 MN4), which has a 1 in 6,000 chance of impacting Earth on April 13 of 2036, 2037, or 2054. Apophis, however, is considerably smaller and lighter than 2004 VD17 and has been assigned a 1 on the Torino scale. 2004 VD17 and Apophis are the only currently observed objects with a Torino value above 0.

Despite the serious consequences of such a large space rock colliding with Earth, it is far too early to worry about an impact from this Near Earth Object. In all likelihood, additional observations will clear the asteroid of any chance of hitting Earth and assign it a 0 Torino value. However, since it will be a while before this asteroid can be observed again, 2004 VD17 is likely to retain its standing on the Torino scale for some time to come.